Skin Diseases That Cause Dark Spots. 1  Melasma: Itâs one of the commonest causes of grayish patches on the face. It mostly affects the forehead, cheeks, or the area between your mouth and nose. 2  Riehlâs Melanosis: It causes grayish or brownish patches on your face resulting from hyper-pigmentation.
In biology, tissue is a cellular organizational level intermediate between cells and a complete organ.A tissue is an ensemble of similar cells from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.The study of tissue is known as histology or, in connection with disease, histopathology.unctions of epithelial tissue: 1  the cells of the body surface form the outer layer of skin. 2  inside the body, epithelial cells form the lining of the mouth & alimentary canal & protect these organs. 3  epithelial tissues help in absorption of water & nutrients.
A tissue is one of the building blocks of an organism--either animal or plant. An organism is comprised of tissues, which are made up of individual cells. These cells share a similar structure (how they're built) and function (what they do).The study of tissues is a field known as histology.pecific epithelial tissue types consist of the combination of the cell shape and number of cell layers. For example, simple cuboidal epithelial tissue describes tissue that is one cell layer thick, with cells that are cube-like in appearance.